The present invention relates to a method and apparatus for making drip irrigation devices, and particularly to such devices including a tube having a plurality of dripper units bonded to a surface of the tube with each unit extending for only a part of the circumference of the tube.
One of the serious problems in making drip irrigation devices of the foregoing type is the bonding of the dripper units to the tube at the time of extrusion of the tube. The dripper units are generally bonded by pressing them against the tube. Ideally, the velocity of the dripper units should be zero relative to that of the tube at the instant of bonding to avoid creating stresses in the bond and/or weakened portions in the tube. This is presently accomplished by accelerating each dripper unit in the axial direction until its velocity reaches that of the tube being extruded, and then displacing the dripper units transversely into contact with the tube when both the tube and the dripper units are travelling at exactly the same linear velocity. However, as a practical matter it is difficult to control the acceleration and transverse displacement of the dripper units to assure that the dripper units will be brought into contact with the tube at the precise instant that both are travelling at the same linear velocity.